Portable audio devices such as consumer electronic audio devices or systems including tablet computers, smart phones, cellular phones, mobile phones, digital media players and the like may use more than one acoustic microphone to receive or input audio from the user's mouth (e.g., a user's voice). In some case, the device may have at least two opposite facing acoustic microphones on opposing surfaces (faces) of the device.
An audio integrated circuit referred to as an audio codec may be used within the audio device, to receive audio signals from multiple integrated microphones of the device, such as during “speakerphone mode”. In addition, the audio codec also includes the capability of outputting audio to one or more speakers of the device. The audio codec is typically equipped with several such audio input and output channels, allowing audio to be played back through any of the speakers and received from any of the microphones.
However, under typical end-user or environmental conditions, a single microphone may do a poor job of capturing a sound of interest (e.g., speech received from a user's mouth) due to the presence of various background sounds. So, to address this issue many audio devices often rely on noise reduction, suppression, and/or cancelation techniques. One commonly used technique to improve signal to noise ratio is audio beamforming. Audio beamforming (also referred to as spatial filtering) is a digital signal processing technique in which sounds received from two or more microphones are processed and combined to enable the preferential capture of sound coming from certain directions. For example, a computing device can form beampattern using two or more closely spaced, omnidirectional microphones linked to a processor. The processor combines the signals captured by the different microphones to generate a single output to isolate a designed sound source from background noise. Such beamforming may be used to more accurately detect a user's voice while in speaker mode.